From 8c8a7cd647c53cd620e702243914820b6eae70f1 Mon Sep 17 00:00:00 2001 From: Huang Tao Date: Mon, 6 May 2024 10:36:07 +0800 Subject: [PATCH] target/riscv: Implement dynamic establishment of custom decoder In this patch, we modify the decoder to be a freely composable data structure instead of a hardcoded one. It can be dynamically builded up according to the extensions. This approach has several benefits: 1. Provides support for heterogeneous cpu architectures. As we add decoder in RISCVCPU, each cpu can have their own decoder, and the decoders can be different due to cpu's features. 2. Improve the decoding efficiency. We run the guard_func to see if the decoder can be added to the dynamic_decoder when building up the decoder. Therefore, there is no need to run the guard_func when decoding each instruction. It can improve the decoding efficiency 3. For vendor or dynamic cpus, it allows them to customize their own decoder functions to improve decoding efficiency, especially when vendor-defined instruction sets increase. Because of dynamic building up, it can skip the other decoder guard functions when decoding. 4. Pre patch for allowing adding a vendor decoder before decode_insn32() with minimal overhead for users that don't need this particular vendor decoder. Signed-off-by: Huang Tao Suggested-by: Christoph Muellner Co-authored-by: LIU Zhiwei Reviewed-by: Richard Henderson Reviewed-by: Alistair Francis Message-ID: <20240506023607.29544-1-eric.huang@linux.alibaba.com> Signed-off-by: Alistair Francis --- target/riscv/cpu.c | 1 + target/riscv/cpu.h | 1 + target/riscv/tcg/tcg-cpu.c | 15 +++++++++++++++ target/riscv/tcg/tcg-cpu.h | 15 +++++++++++++++ target/riscv/translate.c | 31 +++++++++++++++---------------- 5 files changed, 47 insertions(+), 16 deletions(-) diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c index 0d6fb9b4ba..abeb50369c 100644 --- a/target/riscv/cpu.c +++ b/target/riscv/cpu.c @@ -1134,6 +1134,7 @@ void riscv_cpu_finalize_features(RISCVCPU *cpu, Error **errp) error_propagate(errp, local_err); return; } + riscv_tcg_cpu_finalize_dynamic_decoder(cpu); } else if (kvm_enabled()) { riscv_kvm_cpu_finalize_features(cpu, &local_err); if (local_err != NULL) { diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h index 746efd099a..04ab0f153a 100644 --- a/target/riscv/cpu.h +++ b/target/riscv/cpu.h @@ -455,6 +455,7 @@ struct ArchCPU { uint32_t pmu_avail_ctrs; /* Mapping of events to counters */ GHashTable *pmu_event_ctr_map; + const GPtrArray *decoders; }; /** diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c index fedc035313..f59b5d7f2d 100644 --- a/target/riscv/tcg/tcg-cpu.c +++ b/target/riscv/tcg/tcg-cpu.c @@ -863,6 +863,21 @@ void riscv_tcg_cpu_finalize_features(RISCVCPU *cpu, Error **errp) } } +void riscv_tcg_cpu_finalize_dynamic_decoder(RISCVCPU *cpu) +{ + GPtrArray *dynamic_decoders; + dynamic_decoders = g_ptr_array_sized_new(decoder_table_size); + for (size_t i = 0; i < decoder_table_size; ++i) { + if (decoder_table[i].guard_func && + decoder_table[i].guard_func(&cpu->cfg)) { + g_ptr_array_add(dynamic_decoders, + (gpointer)decoder_table[i].riscv_cpu_decode_fn); + } + } + + cpu->decoders = dynamic_decoders; +} + bool riscv_cpu_tcg_compatible(RISCVCPU *cpu) { return object_dynamic_cast(OBJECT(cpu), TYPE_RISCV_CPU_HOST) == NULL; diff --git a/target/riscv/tcg/tcg-cpu.h b/target/riscv/tcg/tcg-cpu.h index f7b32417f8..ce94253fe4 100644 --- a/target/riscv/tcg/tcg-cpu.h +++ b/target/riscv/tcg/tcg-cpu.h @@ -26,4 +26,19 @@ void riscv_cpu_validate_set_extensions(RISCVCPU *cpu, Error **errp); void riscv_tcg_cpu_finalize_features(RISCVCPU *cpu, Error **errp); bool riscv_cpu_tcg_compatible(RISCVCPU *cpu); +struct DisasContext; +struct RISCVCPUConfig; +typedef struct RISCVDecoder { + bool (*guard_func)(const struct RISCVCPUConfig *); + bool (*riscv_cpu_decode_fn)(struct DisasContext *, uint32_t); +} RISCVDecoder; + +typedef bool (*riscv_cpu_decode_fn)(struct DisasContext *, uint32_t); + +extern const size_t decoder_table_size; + +extern const RISCVDecoder decoder_table[]; + +void riscv_tcg_cpu_finalize_dynamic_decoder(RISCVCPU *cpu); + #endif diff --git a/target/riscv/translate.c b/target/riscv/translate.c index 2c27fd4ce1..4cd6480558 100644 --- a/target/riscv/translate.c +++ b/target/riscv/translate.c @@ -35,6 +35,8 @@ #include "exec/helper-info.c.inc" #undef HELPER_H +#include "tcg/tcg-cpu.h" + /* global register indices */ static TCGv cpu_gpr[32], cpu_gprh[32], cpu_pc, cpu_vl, cpu_vstart; static TCGv_i64 cpu_fpr[32]; /* assume F and D extensions */ @@ -114,6 +116,7 @@ typedef struct DisasContext { /* FRM is known to contain a valid value. */ bool frm_valid; bool insn_start_updated; + const GPtrArray *decoders; } DisasContext; static inline bool has_ext(DisasContext *ctx, uint32_t ext) @@ -1123,21 +1126,16 @@ static inline int insn_len(uint16_t first_word) return (first_word & 3) == 3 ? 4 : 2; } +const RISCVDecoder decoder_table[] = { + { always_true_p, decode_insn32 }, + { has_xthead_p, decode_xthead}, + { has_XVentanaCondOps_p, decode_XVentanaCodeOps}, +}; + +const size_t decoder_table_size = ARRAY_SIZE(decoder_table); + static void decode_opc(CPURISCVState *env, DisasContext *ctx, uint16_t opcode) { - /* - * A table with predicate (i.e., guard) functions and decoder functions - * that are tested in-order until a decoder matches onto the opcode. - */ - static const struct { - bool (*guard_func)(const RISCVCPUConfig *); - bool (*decode_func)(DisasContext *, uint32_t); - } decoders[] = { - { always_true_p, decode_insn32 }, - { has_xthead_p, decode_xthead }, - { has_XVentanaCondOps_p, decode_XVentanaCodeOps }, - }; - ctx->virt_inst_excp = false; ctx->cur_insn_len = insn_len(opcode); /* Check for compressed insn */ @@ -1158,9 +1156,9 @@ static void decode_opc(CPURISCVState *env, DisasContext *ctx, uint16_t opcode) ctx->base.pc_next + 2)); ctx->opcode = opcode32; - for (size_t i = 0; i < ARRAY_SIZE(decoders); ++i) { - if (decoders[i].guard_func(ctx->cfg_ptr) && - decoders[i].decode_func(ctx, opcode32)) { + for (guint i = 0; i < ctx->decoders->len; ++i) { + riscv_cpu_decode_fn func = g_ptr_array_index(ctx->decoders, i); + if (func(ctx, opcode32)) { return; } } @@ -1205,6 +1203,7 @@ static void riscv_tr_init_disas_context(DisasContextBase *dcbase, CPUState *cs) ctx->itrigger = FIELD_EX32(tb_flags, TB_FLAGS, ITRIGGER); ctx->zero = tcg_constant_tl(0); ctx->virt_inst_excp = false; + ctx->decoders = cpu->decoders; } static void riscv_tr_tb_start(DisasContextBase *db, CPUState *cpu)